Fission could do direct conversion probably as well.
If only someone things of a reaction where betas are absorbed..
Edit:Umm there is, the problem seems with power
http://en.wikipedia.org/wiki/Atomic_bat ... tavoltaics
Tri-Alpha Rumor
Sure it would be nice but it's not cost effective to do so. If you want to build a few fusion plants as neutron sources to process the long lived fission products that might be feasible if mandated by the government. It doesn't make economic sense to build fusion/fission hybrids for electrical power generation. The cost of nuclear power is already dominated by the capital costs. The cost of the uranium is only 0.22 cents/Kwh, another 0.25 cents/Kwh for enrichment and fuel assembly construction, 1.3 cents/Kwh for operations and maintenance and 5 cents/Kwh for the capital costs of the plant. Nor does it make economic sense to breed fuel, even extracting fissile material from the spent fuel is 4.5 times more expensive than just using freshly mined uranium.Helius wrote: The point of a fusion/fission hybrid is that you can enhance the neutron economy of the reactor. Wouldn't it be nice to return I129 back into the pot? A well designed fusion/fission hybrid can be very cleaning in terms of waste, and actually produce a lot of useful isotopes beside.
I'm not blaming the physics and technology for proliferation, that is largely a political problem. However it IS a political reality and proliferation concerns are why the US currently uses a once through fuel cycle and does no reprocessing of it's fuel. It's also why all the breeder reactor development programs have been shut down. Nothing is going to happen in that direction until the political wind changesI also get a big kick out of those that blame the physics and technology for Nuclear weapons proliferation. It takes 1940's American technology, 1990's *North Korean* technology to produce Nuclear weapons. A modern Fission/Fusion hybrid plant could easily be designed to be so much a higher threshold, that it would be the absolute worst choice for a rogue nation to attempt to use for Nuclear weapons.... Using such a complex and useful power reactor could easily be made the hardest way, and the most visible way to attempt to make nuclear weapons. A good design will force a rogue nation to pursue simpler methods. Why do people keep blaming physics of *more* complex technologies for nuclear proliferation? New reactor designs only need to be a higher threshold than tried and true technologies that everyone knows already works.
The bottom line though is economics. Fusion/fission must compete with existing fission power technology. It either has to generate power more economically or offer some compelling advantage to justify the increased cost. I don't see it doing either unless something like polywell works with aneutronic fusion.
I didn't follow you, Higher Threshold of what?
You're jumping to a conclusion, since we don't even know if Q>1 will happen anytime this century. You can't say 6 neutrons per fission is worth it or not, because there simply isn't enough information to jump to that conclusion either.randomly wrote:Then it will make sense.
A Fusion/Fission hybrid does not.
Maintaining a neutron economy of a fission reactor is a very delicate process with respect to design, and adding neutrons from an electrical source could allow great new possibilities. To dismiss out of hand the economics of fusion enhanced neutron economies is at least dubious.
I'm comparing it to already known reactor technology such as a fluoride molten salt reactor running on a thorium fuel cycle. These already have a sufficient neutron economy to breed more fuel than they use.
What would be the economic advantage of adding all the fusion complexity to the system when it's not needed? Just because it's technically feasible to make these kinds of systems doesn't mean that it makes economic sense.
What scenario do you envision that a fusion/fission hybrid would have an economic advantage over a simple breeder reactor?
What would be the economic advantage of adding all the fusion complexity to the system when it's not needed? Just because it's technically feasible to make these kinds of systems doesn't mean that it makes economic sense.
What scenario do you envision that a fusion/fission hybrid would have an economic advantage over a simple breeder reactor?
Breeding isn't the only issue. As I've asked before, wouldn't it be beneficial to return Iodine 129 back into the reactor? Putting reactor poisons (and biosphere ones) would ruin the neutron economy if you were only relying on 2.5 neutrons per fission. Add a neutron or two from another source, especially really hot ones and you could burn lots of strange isotopic stuff that had no economic value but only economic detriment to it's existence.I'm comparing it to already known reactor technology such as a fluoride molten salt reactor running on a thorium fuel cycle. These already have a sufficient neutron economy to breed more fuel than they use.
It's not needed for the thinnest fission breakeven, but it is needed if you introduced reactor poisons into the reactor; Introducing isotopes you wanted to change. The economic advantage depends on how expensive the secondary neuron source is.What would be the economic advantage of adding all the fusion complexity to the system when it's not needed? Just because it's technically feasible to make these kinds of systems doesn't mean that it makes economic sense.
What scenario do you envision that a fusion/fission hybrid would have an economic advantage over a simple breeder reactor?
You wouldn't put a small reactor under ITER, or the NIF reactor for instance, but if you had a small device that even fell short of breakeven, it might we worthwhile to use it to enhance a fission reactors neutron economy.
A Thorium MSR is NOT a simple breeder. In order to make it function at all you need to remove the Protactinium until it decays into U233. Otherwise it is a poison and ruins the neutron economy. With an external neutron source, the complexity of the rapid fuel recycling gives way to the safety of an "on/off" accelerated reactor. One complexity for another, with safety thrown in.randomly wrote:... What would be the economic advantage of adding all the fusion complexity to the system when it's not needed? Just because it's technically feasible to make these kinds of systems doesn't mean that it makes economic sense.
What scenario do you envision that a fusion/fission hybrid would have an economic advantage over a simple breeder reactor?
INL is a government nuclear laboratory and research facility. They do fuel reprocessing research.ladajo wrote: What do you mean? When is the last time you vacationed in the Eastern Idaho Desert? Must have been some time very recently...
I meant that as a matter of policy the US does not reprocess any of the spent fuel from commercial nuclear power plants.
I was not including laboratory experiments or military use.
The fuel salt only needs to be processed about once every 10 days, the protactinium is separated using a bismuth column. In line reprocessing also allows burning almost all the minor actinides greatly diminishing the high level waste output.KitemanSA wrote:A Thorium MSR is NOT a simple breeder. In order to make it function at all you need to remove the Protactinium until it decays into U233. Otherwise it is a poison and ruins the neutron economy. With an external neutron source, the complexity of the rapid fuel recycling gives way to the safety of an "on/off" accelerated reactor. One complexity for another, with safety thrown in.
I don't see how an external neutron source is going to let you avoid fuel reprocessing if you want to use thorium as a feedstock. How do you propose using thorium without doing protactinium separation?
If that is unpalatable to you there are other options for using a plutonium breeder instead such as a liquid metal cooled fast reactor. Neutron economy in a fast reactor has a great deal of headroom.
There are a lot of options in nuclear reactors that address the problems without adding in the extra expense and complexity of a fusion based neutron generator. The technology is there, the problem has been the political concern about proliferation and security of the production of weapons usable material.
If you have a particular fusion/fission system in mind that has clear cost and/or operational advantages over fission reactor technology please describe it.
There has been considerable discussion of this topic here during the 2+ (is that all?) years this board has been here.New technologies only need to be a higher threshold of difficulty in making nuclear weapons, over the tried and true methods already established.
The general thought is that a BFR would make proliferation some easier. Building a BFR (once it is known to work) will be easier and less hazardous than building a fission nuke. And it turns on and turns off at the flick of a switch. So unlike a nuke you don't have to plan for continuous neutron flux while loading and unloading starting material. And 3 days (Xe poisoning) between restarts. And you don't have to worry about criticality accidents.
Engineering is the art of making what you want from what you can get at a profit.
To be clear, ECF, and CPP at INL have been reproccessing military and some civilian cores since they were built. As you mentioned they are government facilities. The primary focus on the research side conducted while disassembling and making the spent fuel ready for CPP has been studying the fuel assemblies in order to make new ones better for burn efficiencies, as well as studing core burn patterns against rod programming in order to maximize core lifes. This is done in conjuntion with reprocessing the fuel assemblies. The other practical effect is that there is not enough infra structure to include full scale civilian plant reprocessing at this time, and no one wants to front the money due to the costs incurred to meet political considerations. I agree with your point on the politics of it all, but do not miss that the foundatoin of politics is money. Standing up a civilian nuclear fuel reprocessing program would be way over priced (caused by money as a weapon), and a very complicated path. This is how the Tree Huggers killed our industry in its child hood. Well played media hype...randomly wrote:INL is a government nuclear laboratory and research facility. They do fuel reprocessing research.ladajo wrote: What do you mean? When is the last time you vacationed in the Eastern Idaho Desert? Must have been some time very recently...
I meant that as a matter of policy the US does not reprocess any of the spent fuel from commercial nuclear power plants.
I was not including laboratory experiments or military use.
A fair point made earlier, fusion programs need to watch out, the Tree Huggers are still out there, and they are richer and older now.